A vehicle such as an automobile is provided with a gas treatment device such as a catalyst converter for removing a harmful substance such as carbon monoxide, a hydrocarbon, or a nitrogen oxide in the exhaust gas of a gasoline engine, or a diesel particulate filter (DPF) for removing a particle in the exhaust gas of a diesel engine. Available as the catalyst converter is, for example, a catalyst converter provided with a tubular catalyst carrier, a tubular casing made of a metal for housing the catalyst carrier, and a mat-shaped holding material made of inorganic fibers placed between the catalyst carrier and the casing. One of the functions required for the holding material is to prevent the detachment of the catalyst carrier from the casing.
In view of the foregoing, in Patent Literature 1 for example, it has heretofore been proposed that inorganic particles are adhered and fixed to the outer surfaces of ceramic fibers constituting the holding material to form an irregular structure, thereby increasing the frictional resistance of each of the ceramic fibers.